Solutions Homogeneous mixtures that may be solid, liquid or gaseous Solute: The part of the solution that is dissolved Solvent: The part of the solution that does the dissolving Water is known as the universal solvent The substance there is the most of is typically the solvent!

Rate of Solution Stirring: Speeds up the rate of solution –Fresh solvent is continually brought into contact with the surface of the solute Temperature: Higher temperature leads to higher rate of solutions –Particles move faster which brings the solute & solvent together more quickly

Particle Size: More surface area leads to a faster rate of solution –Powdered sugar dissolves faster than a sugar cube Rate of Solution

SOLUBILITY The amount of solute that dissolves in a given quantity of a solvent at a specified temperature and pressure to produce a saturated solution Unit: grams of solute per 100 g of solvent g solute/100 g solvent

SATURATED SOLUTION Contains the maximum amount of solute for a given quantity of solvent at a constant temperature and pressure –If additional solute is added to a saturated solution, it will not dissolve –At a state of dynamic equilibrium; the rate of solution equals the rate of dissolution

UNSATURATED SOLUTION A solution that contains less solute than a saturated solution at a given temperature and pressure –If additional solute is added to an unsaturated solution, the solute will dissolve until the solution is saturated.

SUPERSATURATED SOLUTION A solution that contains more solute than it can theoretically hold at a given temperature If solute is added to a supersaturated solution, the crystal will increase in size as more solute precipitates out of solution

Miscible: Two liquids that will dissolve in each other in all proportions –Any amount of the liquids will dissolve –Example: Ethanol & Water Immiscible: Liquids that are insoluble in one another –Example: Oil & Vinegar

FACTORS AFFECTING SOLUBILITY Temperature –The solubility of most solids increases as the temperature of the solvent increases –The solubility of most gases is greater as the temperature of the solvent decreases

Pressure: Does not effect solid or liquid solubility Gas solubility increases as the partial pressure of the gas above the solution increases FACTORS AFFECTING SOLUBILITY Henry’s Law: At a given temperature, the solubility(S) of a gas in a liquid is directly proportional to the pressure (P) of the gas above the liquid S 1 = S 2 P 1 P 2

SOLUBILITY CURVES Graph that illustrates the grams of solute that dissolves in 100 g of water at a given temperature –The Line: A saturated solution (# of grams that can dissolve in 100 g water at that temperature) –Above the line: A supersaturated solution –Below the line: An unsaturated solution SOLUBILITY QUESTIONS 1)What happens to the solubility of KNO 3 as the temperature increases? 2)50 g of KNO3 is dissolved in 100 g of water at 30ºC. Is this a saturated, unsaturated or supersaturated solution? 3)20 g of KNO3 is dissolved in 100 g of water at 60ºC. Is this a saturated, unsaturated or supersaturated solution? 4)How much KNO 3 will dissolve at 50ºC? 5)How much KNO 3 will crystallize if the temperature is lowered from 40ºC to 10ºC? 6)A saturated solution of KNO 3 is prepared in 100 g of water at 30ºC. If the solution is heated to 70ºC, how much more KNO 3 must be added to obtain a saturated solution?

1)Which substance shows a decrease in solubility as temperature increases? 2)Which substance exhibits the least change in solubility? 3)Which compound is most soluble at 10ºC? 4)Which compound is least soluble at 50ºC? 5)Assuming no supersaturation, how many grams of K 2 Cr 2 O 7 crystallizes if a warm solution containing 50 g of K 2 Cr 2 O 7 in 100 g of water is cooled to 10 ºC?

The concentration is a measure of the amount of solute that is dissolved in a given quantity of solvent –Dilute Solution: One that contains a small amount of solute –Concentrated Solution: One that contains a large amount of solute

Molarity (M) The number of moles of solute dissolved in 1 Liter of solution Molarity (M) = moles of solute liters of solution Examples: 1)A solution has a volume of 2.0 L and contains 36.0 g of glucose (C 6 H 12 O 6 ). What is the molarity of this solution? 2) How many grams of calcium chloride are needed to make 250 mL of a 2.0 M solution of calcium chloride?

DILUTING A SOLUTION M 1 V 1 = M 2 V 2 M = Molarity, V = Volume Examples: 1)How many milliliters of aqueous 2.00 M MgSO 4 solution must be diluted with water to prepare mL of aqueous M MgSO 4 ? 2)How could you prepare 250 mL of 0.20 M NaCl using only a solution of 1.0 M NaCl and water?

PERCENT SOLUTION Another way to express the concentration of a solution 1)As the ratio of the volume of the solute to the volume of the solution % by Volume = Volume of Solute x 100% Volume of Solution 1)As the ratio of the mass of the solute to the mass of the solution % by Mass = Mass of Solute x 100% Mass of Solution

PERCENT SOLUTION EXAMPLES 1)What is the percent volume of ethanol (C 2 H 6 O, or ethyl alcohol) in the final solution when 85 mL of ethanol is diluted to a volume of 250 mL with water? 2)A bottle of the antiseptic hydrogen peroxide (H 2 O 2 ) is labeled 3.0% volume. How many mL H 2 O 2 are in a mL bottle of this solution? 3)Suppose you want to make 2000 g of solution of glucose in water that has a 2.8% by mass concentration of glucose. How much glucose should you use?

MOLARITY Example: A solution has a volume of 2.0 L and contains 0.36 mol of glucose (C 6 H 12 O 6 ). What is the molarity of the solution? Example: Mass of Kool-Aid needed for 0.1 M solution?